VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Engine Rear Seal

Can the engine rear seal on a 1942 coupe be easily replaced without taking the engine out of the car? How about the rear seal on the transmission?

Good Morning,

What a can of worms you are asking about? Fortunately for you we have had good discussions on both topics, and you can find them doing searches of our past posts. If you haven't done any you need to put your "big boy pants on" and try. Both leaks are best ignored unless they are severe, or you are rebuilding your engine or dealing with transmission problems. Because this is only your 9th post. I would go real slowly at seeing these leaks as priorities.

The easy question to answer is about transmission seals (gaskets). All rear seals/gaskets between the transmission and drive shaft will require you to remove the universal joint. There are three seals on the torque tube. One is at the rear of the tube where the drive shaft mates with the tube. The other two are at the ball area of the torque tube where the tube and transmission mate. You can order a kit from Chevs of the 40's or the Filling Station to do this repair. I have included a link to some posts discussing this topic. 29-54 Torque Tube Gasket

I spent at least three years dealing with a leaking rear engine seal. I did it because I am anal about any leaks and my leak was causing clutch pressure plate issues commonly described as chatter. After dealing with the problem my "big boy pants" fit way to loose. I think I solved the problem with a $5000 engine rebuild.

Some will tell you how they took a special tool called a "Sneeky Pete" and fished their old seal out and then magically threaded a new one in place. Some will tell you they just replaced the bottom part of the seal and that took car of the leak. Some will tell you you need to find an original asbestos seal to solve the leak that the new seals just don't work, and finally some will say a small leak is normal and you can only solve your problem by not running oil in your engine! I and others have well documented our experiences with this topic.

Good luck, Mike

P.S. Hopefully you have already read these November post. My New Forty-Two

The information on the torque tube was exactly what I was looking for-thanks Mike Butler.

I have replaced the rear main seal on my 1951 216 and it was successful. However, I replaced the main bearings at the same time and adjusted them to the minimum clearance. I did all this with the engine in place.

One solution to rear engine seal leaks that I have never seen on this forum is documented in the Clymer book, Cast Iron Wonder … Chevrolets fabulous Six, authored by Doug Bell. This was a short cut used by “flat raters” … mechanics that used “unconventional practices” to shorten the time for a job in return for financial considerations. Bell claims that Chevy had more than its fair share of flat raters in the repair business.
In the case of bad oil leaks, this apparently worked very well. They held two hacksaw blades together and used them to cut a channel in the lower half of the rear bearing shell … from the oil groove forward towards the front of the bearing. This gave an easy route for the oil to flow back into the pan. This should work both with slingers and rear seal versions. Then the bearing would be reshimed to spec, the breather cleaned out and the customer would drive away happy about his oil consumption. I would say easily a 1 hour job.

I have recently rebuilt my 39 engine so I have had no incentive to try this flat rate job yet but I think it may have a place for some members as an alternative to chasing the top seal.

I did that to my '39 and it stopped the leak. This was about 15 years ago and still doing fine.

Great idea, thanks for sharing. I think I will try it on my 31.

God Morning,

I thought the 1939 engine did not have a rear seal? So are we really going to get the same effect on our 41 rear bearing cap with a rear seal?

It may have taken a "flat rater" an hour to do this job but it could easily take you 6 or more hours if the engine has not had the oil pan cleaned in a few years. I would want to do a thorough cleaning of my oil pan and oil pump screen. This can be time consuming. I might even want to follow the manuals recommendation and re-aim my oil nozzles. Removing the oil pan and prepping the oil pan gasket surfaces then reinstalling the oil pan also could amount to a good hour of work.

You would also need to remove the rear main bearing to cut the groove in it which could disrupt the mating of the two rear seals on each side causing an additional oil leak?

While I am intrigued by the groove idea I would like to know of others that have performed this to their 41 and newer rear bearing, and what were their results?

The picture below shows a 41 vintage rear bearing cap. I assume you are recommending cutting the groove at the point of the red arrow? A band of metal about 1/8th of an inch wide. Doing the cut with hacksaw blades seems like it could be better accomplished with today's technology, the cutting disk on a Dremel?

Seems like we need to do some more research on the success of this method for solving rear main seal oil leaks on 1940 and newer 216 engines?

Thanks, Mike

The '39 engine was the last to not have a seal. The grove is cut in the front half of the bearing up to the oil grove so more pressand flow is released forward.
It should work equally well on a seal engine.
My '39 has been driven long and hard with no beraing failure.
The grove is cut in the front of the insert, not the cap.

The groove is actually cut into the bearing insert not the cap.
The difference between a line mechanic working on flat rate is a whole different can of worms than a car owner tinkering in his home shop. They get paid by what they accomplish. You also have to remember that the flat rate guys are usually working on cars that are anywhere from 5 years old to a new car. Some of the long term issues are really non issues for them, re: sludge in the pan type things. Hope this makes sense.

Thanks guys,

A picture is worth a thousand words. Here is another one with the bearing insert. Please tell me where you would cut the groove? I kind of assume it is between the oil groove in the insert and the the area closest to the edge of the insert, by my socket?

Thanks, Mike

First I`ve read about this fix on Chat .....maybe I missed it ....I did the compression of the upper rope seal adding some new rope to the compressed area and then putting new rope in lower cap. It slowed down the drip in the beginning and is still not bad , but is not dry by any means. If I ever drop the pan again I might give this one a try .Always something new to learn on the Chat !!

I did post this "fix" a couple of times over the years.

Mike,
From tne little circle (bottom-center) to the front of the engine.
I did mine about 1/4" off center as the bottom center takes most of the load.

Thanks, Gene,

The info on having the groove off center is also very important. Did you notice I found a cap with an insert that was stamped GM in the oil groove? The insert looks real good. I wonder if it was original to the engine or replaced in a rebuild?

Thanks, Mike

P.S. I saved all of the caps and cap inserts from the engine the cap came from. I parted the block out last summer. It was in great condition except for a long crack in the water jacket on the driver's side of the block. Every once and a while I get a call from someone needing a replacement cap.

Mike,

On my 47 216 I had my block machined to accept a 1-piece rear main seal.

In addition, a groove was cut precisely where your red arrow is pointing to help the flow of oil stay away from the seal.

I had this done over 2 years ago and it's perfectly dry.

Thanks Fleetboy,

I am glad we are rehaving this discussion, and to hear of your results. I want to update everyone on some of the past discussion we have had on this topic. If anyone has a memory like mine you may have forgotten a lot of it. These posts are just the tip of the iceberg for me on dealing with a leaking rear seal. Like I originally said to 42special dealing with a leaking real seal is "opening a can of worms." Thank goodness we have an index of our past posts!

1948 rear main seal

Update on 1941 rear seal

Re: rear main seal problem

Thanks, Mike

When I corrected the rear main seal leak on my 1950 I did not cut a grove in the bearing. Reason; On the 1950-1957 235 engines with hydraulic lifters the oil pressure is fed from the rear main bearing to the camshaft bearing (as is a 216) but from the cam bearing it goes to the rocker arm line and also the hydraulic lifter gallery. I was afraid the lifter gallery would may not get enough volume of oil to keep the lifters filled.
Probably would work on a full pressure engine but with 15 pounds of pressure I was a litle doubtful.

Fleetboy,

I like the idea of a one-piece rear main seal, but I've always wondered what provision, if any, is made for adding/removing shims to adjust the rear main bearing clearance, as this would change the effective bore of the seal cavity.

Mark

I am currently building two different 216 engines, both using a one piece rear main oil seal. One is a 1940 and the other is a 1948. My goal is to write a technical article for the G&D explaining the entire process.

dtm

Probably a dumb question, but....

Is the oil building up inside that chamber (between the bearing and the gasket) rather than flowing down back into the pan? Looks to me like if that area is filled with oil, it would prevent any additional oil from going in that direction...

Too bad my Dad got rid of the donor engine (it was pretty worn out), otherwise I would have taken it apart to study the bearing setup....

Hi Jim,

In the above picture with the red arrow you will see a faint round shadow in the groove in front of where the rear seal is pressed in place. That round shadow is a 1/4 inch hole that drains oil from this area into the oil pan. So there is no buildup of oil there. Only the constant spray of oil throughout the area as the engine runs. We have had discussion with some saying oil may be leaking under the rear seal at the top of the crank or even under the crank, and others saying it leaks where the seals mate.

If you would like me to take a picture of the cap from a different angle let me know.

Thanks, Mike

Note that the 1939 and prior has no seal and is not the same animal.

Ah, that answers my question, thanks!


[quote=Chev Nut] Note that the 1939 and prior has no seal and is not the same animal.

Just looked up group #0.137, says '40 & '41, so you are correct, I don't have the oil seal. Since I haven't seen my bearings off the car, what prevents oil from leaking out back there?

The oil slinger on the crankshaft slings the oil into the deep grove in the block and main bearing cap. The bottom of the grove (in the cap) has oil return holes that allow the oil to return to the pan. If the bearing is too looose to much oil can pass by and the system can't handle the volumn.....that plus some other things can cause a leak.